lovecindydw
花朵
共回答了21个问题采纳率:85.7% 举报
1.cos225°=cos(180°+45°)=-cos45°=-√2/2
2.sin(11π/3)=sin(4π-π/3)=sin(2π+2π-π/3)=sin(2π-π/3)=-sinπ/3=-√3/2
3.sin(-16π/3)=-sin(16π/3)=-sin(2π+2π+π+π/3)=-sin(π+π/3)=-(-sinπ/3)=sinπ/3=√3/2
4.cos(-2040°)=cos2040°=cos(1980°+60°)=cos(360°*5+180°+60°)=cos(180°+60°)=-cos60°=-1/2
灵活的运用公式一到四可以将很大的数化为-180°~180°以内的数,这样就可以化繁为简,根据特殊三角函数值,得出结果.
1年前
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